Sleeved deep draw cushion for punch presses



April 28, 1964 H. L. STEGNER 3,130,962

SLEEVED DEEP DRAW CUSHION FOR PUNCH PRESSES Filed Nov. 20, 1961 3 Sheets-Sheet l Fig. l

INVENTOR. HARVEY L. STEGNER A ril 28, 1964 H. STEGNER 3,130,962

SLEEVED DEEP DRAW CUSHION FOR PUNCH PRESSES Filed Nov. 20, 1961 3 Sheets-Sheet 2 Fig. 3

INVENTOR. HARVEY L. STEGNER April 28, 1964 H. L. STEGNER SLEEVED DEEP DRAW CUSHION FOR PUNCH PRESSES 3 Sheets-Sheet 3 Filed Nov. 20, 1961 l w l l I I I LIIIIVIIIIIL INVENTOR.

HARVEY L. STEGNER BY United States Patent Ofifice 3,130,962 Patented Apr. 28, 1964 3,130,962 SLEEVED DEEP DRAW (IUSHIQN FOR PUNQH PRESSES Harvey L. Stegner, 2235 Cliif St., San Diego, Calif. Filed Nov. 20, 1961, Ser. No. 153,339 3 Claims. (Cl. 267--1) This invention relates to the shaping of metals, and more particularly to apparatus that facilitates the production of shapes that are relatively deep.

Background In order to form metals into certain shapes, such as cups and the like, a flat sheet of metal may have its central portion punched to the desired depth, diameter, and curvature dimension. To accomplish this result, a machine known as a punch press is used; the movable ram of some punch presses developing forces measured in the hundreds of tons for shapin relatively thick sheets of metal. To produce deep cups, the shaping process frequently requires that the metal be stretched, or drawn; and deep-drawn shapes tend to acquire undesired wrinkles and deformations.

It has been found that, to a certain extent, the deformations may be minimized by controlling the stretching forces; two ways of doing this being possible. The first requires that the movement of the punch press ram be controlled; but this necessitates different settings for various materials, thicknesses, and ultimate shapes. The second method of control comprises establishing a cushion against which the material is forced, thus producing a controllable resistive force.

One prior-art cushion used liquids, and since liquids are substantially incompressible, controlled the resistive force by varying the rate of escape of the liquid. This arrangement became quite complex, and required valves, cams, tanks, connecting tubes, mechanical linkages, and the like. Another prior-art cushion used a resilient material; but this had the disadvantage that the resistive force varied in a given non-controllable manner.

Objects and Drawings It is therefore the principal object of my invention to provide an improved apparatus for shaping metals.

It is another object of my invention to provide improved apparatus for controlling the force used in shaping metals.

It is a further object of my invention to provide an improved cushion for a punch press, said cushion comprising a bellows.

It is a still further object of my invention to provide means for stabilizing the bellows of the cushion against irregular undulation or squirming, even when used with a deep drawing punch press.

The attainment of these objects and others will be realized from the following specification, taken in conjunction with the drawings, in which:

FIGURE l is a fragmentary, diagrammatic view, partially cross sectional, of a punch press incorporating my invention;

FIGURE 2 is a top plan view, partially cross sectional, of one embodiment of my invention;

FIGURE 3 is a partially cross sectional view taken along line 33 of FIGURE 2; and

FIGURE 4 is a partially cross sectional view of another embodiment of my invention.

Detailed Description of the Invention The basic concept of my invention will be understood from FIGURE 1, wherein a blank or workpiece comprising a flat sheet of metal is to be formed into some configuration such as an inverted cup-shape. To accomplish this result, workpiece 10 is positioned on a vertically movable blank-supporting template 12. When the punch press is actuated, its ram 13 descends, causing pressure element 14 to descend, and pinch the edges of workpiece 10 between the lower surface of pressure element 14 and the upper surface of template 12.

Pressure element 14 may take any one of many forms, one of the most widely used forms being a block of resilient material such as rubber. As pressure element 14 descends further, template 12 is forced downward; being restricted to vertical movement by means such as guide rods 16, which are slidable through bores in the bolster or bed 18, of the punch press.

When the template 12 descends below the uppermost portion of die 20, the central portion of the workpiece 10 is prevented from moving downward by the die, while the peripheral portions of the workpiece are carried downward by the pinching effect of pressure element 14 and template 12. It may thus be seen that workpiece 10 is conformed to the shape of die 20.

Two shortcomings now arise. First, the periphery of workpiece 10 tends to be pulled inwards, despite the pinching eifect of the pressure element and the template. Sec- 0nd, the uncontrolled downward movement of pressure element 14 introduces unwanted distortions into the workpiece.

My invention overcomes both of the above shortcomings. It comprises a cushion 22 that provides controlled resistance to the downward movement of the workpiece, and thus minimizes the amount of distortion introduced therein.

My cushion 22 comprises two or more support rods 24 that have one end fastened to a top attachment plate 25 that is secured to bolster 18, and have their other ends supporting a bottom flanged ring 32, said top attachment plate, bottom flanged ring and support rods defining a cage for a sealed bellows 26, preferably of metal, which is positioned interiorly or between support rods 24. Bellows 26 has upper and lower end plates 28 and 3% respectively, the lower end plate 30 resting on the flanged ring 32, and the upper end plate 28 seating against top attachment plate 25. The construction of bellows 26 per se may be conventional, and contains a given volume of air.

My invention operates as follows. As pressure element 14 descends, it gradually depresses template 12, causing guide rods 16, which rest on the upper end plate 28, to depress the end plate and thus compress the bellows 26. This causes the air in the bellows to be compressed to a smaller volume, thus gradually increasing the pressure with which it resists the downward movement of template 12 and workpiece It).

This has three distinct advantages. First, as the workpiece approaches its final shape, the resisting force increases, thus slowing down the shaping or forging action. Second, as the pressure element 14 descends, the increasing resistive force produces a stronger pinching action between pressure element 1.4 and template 12, thus holding the periphery of the workpiece progressively more firmly in place. Finally, when the pressure element 14 has finished its downward stroke and the shaping of the workpiece and begins to move upwardly, the upward movement of the end plate 28 of the bellows raises the workpiece oil? die 20.

It will thus be realized that my cushion overcomes the shortcomings of prior-art liquid cushions in that it is extremely simple, does not require cams and linkages to control the escape of liquids, and does not require tanks for the storage of the liquid.

It also has an advantage over prior-art resilient cushions, in that the volume of air within the bellows may be eontrolled; and thus the amount and rate of increase of the resistive force may be readily controlled.

There are many instances when the workpiece is to be drawn to the shape of a relatively long cylinder. This requires that the pressure element, the template, the guide rods, and the upper face of the bellows have a relatively long stroke or movement. The bellows, in turn, must be appreciably longer than the stroke; and there is a possibility that the convolutions of the bellows might undulate or squirm, rather than remaining aligned vertically with the adjacent convolutions. This undulation or squirming of the bellows is undesirable because it weakens,- and may permanently deform the bellows.

FIGURES 2. and 3 show one embodiment of my invention for obviating these perils. in this form, bellows 26 has a stabilizer 34 that minimize the danger of undulation.

Basically, stabilizer 34 comprises two sleeves 36 and 33 that telescope into each other. Sleeves 36 and 38 are positioned internally of the bellows 26, and have their distal ends attached to upper and lower end plates 28 and 39 respectively. As shown, sleeve 36 has its proximal end of reduced diameter, so that it will slidably fit into the proximal end of sleeve 38.

In operation, the upper end plate 28 of bellows 26 moves dovmward toward the lower end plate 39 as previously described. The movement of the upper end plate compresses the convolutions of the bellows, which may tend to squirm. This squirming, however, is prevented when the inner surface of the bellows touches the outer surfaces of stabilizer 34.

As the upper end plate 28 moves farther downward, the lower end of sleeve 36 slides progressively farther into lower sleeve 38, thus maintaining the squirm-preventing operation of the stabilizer.

Stabilizer =34 is preferably pierced by apertures 49 to permit equalization of the air pressure in the bellows, and to remove the eiiects of air pressure on the stabilizer itself.

It was previously indicated that the volume of air in the bellows may be controlled to vary the resistive force developed by the bellows. This result is readily achieved by use of a pressure regulator 42 connected between a source of pressurized air, not shown, but indicated by the pipe 44, and bellows 26. If a large resistive force is desired, air is admitted into bellows 26 to a pressure indicated by gauge 46 whereas if a smaller resistive force is desired, air may be bled from the bellows through outlet 48.

Under some conditions the cyclic compression and relaxation of bellows 26, and the cyclic pressure of guide rods 16 may tend to rotate the bellows. Since the bottom plate of the bellows is afiixed to the air lines, this rotational tendency may introduce torsion strains into the structure of the bellows.

The embodiment of my invention shown in FIGURE 4 obviates this danger. Here stabilizer b is also of the telescoping-sleeve type, comprising an upper sleeve 52 and a lower sleeve 54.

Lower sleeve '54 is similar to the lower sleeve of FIG- URE 3, except that its upper end rather than terminating in a smooth circle, is digit-ated; that is, it terminates instead in a series of upwardly-extending fingers 56 separated by downwardly extending notches.

Upper sleeve 52, while actually a unitary structure, may be thought of as a first or inner sleeve and a second or outer sleeve. The first sleeve 60 is slightly smaller than lower sleeve 54, and slidingly coacts therewith as explained in connection with FIGURE 3. The second, or guide, sleeve 6-2 of the upper sleeve is slightly larger and contiguously encircles inner sleeve 60, is d-igitated and terminates in downwardly-extending fingers 64 separated by upwardly-extending notches, and is of substantially the same diameter as lower sleeve 54. Fingers 64 and the separating notches of upper composite sleeve 52 are complementarily spaced with respect to fingers 56 and the notches of lower sleeve 54 and the fingers of the upper and lower sleeves are interdigitated, that is, the fingers of each sleeve are slidably positioned in the notches of the other sleeve.

In use, as the bellows is compressed and extended, the fingers of each sleeve slide along the notches of the other sleeve. The lower sleeve 54 and the pressure sleeve 69 act primarily as an =anti-squirming means, while the interdigital relation of the lower sleeve 54 and the guide sleeve 62 act to prevent twisting of the bellows. Thus, stabilizer 5t? prevents the introduction of torsional strain-s, while constantly maintaining a squirm-preventing engagement.

As in the previous embodiment, bellows 26 may be inflated to any desired pressure before the shaping process is started.

Advantages My invent-ion has sevenal important advantages over prior-art apparatuses. It is formed of simple, readily available components. It can be used with most current punch presses. It efi'ectively controls the shaping function of the punch press. And finally, its resistive force can be easily adjusted by merely introducing into, or bleeding air from, the bellows.

It is understood that minor variation from the form of the invent-ion disclosed herein may be made without depart-ore from the spirit and scope of the invention, and that the specification and drawing are to be considered as merely illustrative rather than limiting.

I claim:

1. A cushion for use with a punch press having a bed plate and a ram, comprising:

an air-tight bellows having an upper end plate and a lower end plate; an open cage enclosing said bellows and having a top attachment plate secured on the underside of said bed plate, and means for supporting said lower end plate;

means for transmitting down-Ward movement of said ram to said upper end plate and thus causing the air in said bellows to be compressed to develop a resistive force; and

stabilizing means positioned internally of said bellows for preventing squirming of said bellows, said stabilizing means comprising a pair of telescoping sleeves having their distal ends attached to said end plates; said sleeves being apertured to equalize pressure inside and outside said sleeves.

2. A cushion for use with a punch press having a bed plate, comprising:

atop attachment plate secured to said bed plate;

a plurality of downwardly extending support rods having one end thereof attached to said punch press;

a support ring attached to the other end of said support rods;

an air bellows having an upper end plate and a lower end plate, said lower end plate being positioned on said support ring, said upper end plate being adjacent said top attachment plate and free to move and compress the air in said bellows, producing a resistive force; and

bellows stabilizing means positioned within said bellows for preventing squirming of said bellows, said stabilizing means comprising a pair of telescoping sleeves attached at one end to the respective end plates.

3. A cushion for use with a punch press, comprising:

a plurality of support rods having one end thereof attached to said punch press;

a support ring attached to the other end of said support rods;

an air bellows having an upper end plate and a lower end plate, said lower end plate being positioned on said support ring, said upper plate being free to move and compress the air in said bellows, producing a resistive force; and

bellows stabilizing means positioned within said bellows for preventing squirming of said bellows, said stabilizing means comprising a pair of telescoping sleeves attached at one end to the respective end plates, one of said sleeves having an unattached digitated end, the other of said sleeves having a pressure sleeve and a guide sleeve having an unattached digitated end, said digitated ends being interdigitated to prevent twisting of said bellows.

References Cited in the file of this patent UNITED STATES PATENTS Guest Apr. 11, 1916 Rode Aug. 19, 1930 Holland Oct. 23, 1945 Greenwood May 22, 1962 FOREIGN PATENTS France Aug. 8, 1938 France June 3, 1940 Great Britain Mar. 8, 1944 

1. A CUSHION FOR USE WITH A PUNCH PRESS HAVING A BED PLATE AND A RAM, COMPRISING: AN AIR-TIGHT BELLOWS HAVING AN UPPER END PLATE AND A LOWER END PLATE; AN OPEN CAGE ENCLOSING SAID BELLOWS AND HAVING A TOP ATTACHMENT PLATE SECURED ON THE UNDERSIDE OF SAID BED PLATE, AND MEANS FOR SUPPORTING SAID LOWER END PLATE; MEANS FOR TRANSMITTING DOWNWARD MOVEMENT OF SAID RAM TO SAID BELLOWS TO BE COMPRESSED TO DEVELOP A RESISTIVE FORCE; AND STABILIZING MEANS POSITIONED INTERNALLY OF SAID BELLOWS FOR PREVENTING SQUIRMING OF SAID BELLOWS, SAID STABILIZING MEANS COMPRISING A PAIR OF TELESCOPING SLEEVES HAVING THEIR DISTAL ENDS ATTACHED TO SAID END PLATES; SAID SLEEVES BEING APERTURED TO EQUALIZE PRESSURE INSIDE AND OUTSIDE SAID SLEEVES. 